1. Field of the Invention
This invention relates to fabrication of integrated circuits on a semiconductor wafer, and more particularly to controlled application of fluids, such as photoresist developer fluids, to a semiconductor wafer surface.
2. Description of the Related Art
In semiconductor fabrication of integrated circuits (ICs), a workpiece, such as a semiconductor wafer, is often treated or sprayed with a fluid as a part of the fabrication process. For example, a surface of a semiconductor wafer can be coated with a photoresist material and cured, after which time the material can be selectively exposed to light or to a charged particle beam. The cured material can be immersed in a photoresist developer to develop and thus selectively expose portions of the wafer surface to produce a desired pattern. The selectively exposed portions can be subjected to chemical vapor deposition, chemical etching, ion implantation or some other semiconductor fabrication process. This process can produce a layer of a circuit or a resistive or conductive component for the IC.
In a similar manner, a liquid dielectric can be sprayed on a selected region of a semiconductor wafer to provide electrical insulation for subsequently deposited IC layers. A liquid or gaseous coating can be sprayed on a selected surface of a metal or plastic substrate for protective purposes. A photographic developer or fixer liquid can be sprayed on a light-sensitive surface of a substrate to develop or fix a previously exposed optical image. In any of these fabrication steps, it is important to apply the fluid as uniformly as possible to the surface or workpiece to help insure that chemical reaction or bonding of the fluid with the exposed surface is not affected by locally non-uniform concentrations of such fluid.
What is needed is an approach that allows monitoring of the spray pattern of a fluid being applied to a surface of a workpiece, to determine whether the fluid is being applied uniformly, or being applied in a selected non-uniform pattern. Preferably, this approach should provide information on the fluid spray pattern that aids in determining how, if at all, the spray pattern should be altered to provide more uniform (or selected non-uniform) application of the fluid to the chosen surface.